The invention relates generally to an applicator device for applying a viscous material, such as nail varnish.
One form of applicator device for applying a viscous material such as nail varnish comprises a container for containing the viscous material to be applied, with a feed duct for feeding the viscous material from the container to an applicator member. Disposed between the outlet opening of the container and an inlet opening of the feed duct is a control valve which can be actuated in the direction of opening thereof, from the exterior of the device. The device further includes a pressure compensation opening for communicating the interior of the container with the exterior of the device, to compensate for variations in pressure within the container. An applicator device of that nature is to be found for example in British patent specification No. 531 741. In that design, pressure compensation which is required as the container is progressively emptied of its material is effected as between the interior of the container and the exterior thereof, either by way of the path along which the viscous material flows from the container to the applicator member or by way of a path which is separate therefrom. In the first-mentioned situation, the viscous material may suffer from a drying-out phenomenon in the flow passage involved, as may occur for example after the applicator device has been unused for a prolonged period of time, with the result that the passage for carrying the feed of material to the applicator member becomes clogged and the device is then useless. In the second possible design configuration with a separate path for pressure compensation purposes, it is possible for the material in the container to dry up in a relatively short period of time because in that case the vent passage is in direct fluid communication with the interior of the container at all times.
In another form of applicator device of the general kind referred to above, the device may include a metering pump with the control valve being integrated in the metering pump construction. In such metering pump arrangements, the pressure compensating opening is separate from the path through which the viscous material flows to the applicator member. Now, in any construction where the pressure compensating opening is separate from the flow path for the viscous material to be applied by way of the applicator member, there is the danger that, in the event of an increased pressure in the container, the viscous material may pass to the pressure compensating opening by flowing through various constrictions and clearances in the arrangement, and may then block the pressure compensating opening. The smaller the diameter of the pressure compensating opening, the more serious is the risk of its becoming blocked in that fashion.
Another form of applicator device is to be found in German patent specification No. 811 861. That device includes a container for the material to be applied, having an applicator member and a passage for feeding the material to be applied to the applicator member. That device further includes a vent duct and a control valve, by means of which the interior of the container can be brought into fluid communication with the exterior of the device, by way of the vent duct. The vent duct also has a receiving chamber therein, to prevent the material in the container from being discharged through the vent duct.